{"id":"F2005L03140","name":"AD/ARRIUS/12 - Check-Valve Piston O-Ring","slug":"ad-arrius-12-check-valve-piston-o-ring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":134339,"registerId":"commonwealth-F2005L03140-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Turbomeca Turbine Engines - Arrius Serie","sectionType":"division","heading":"Turbomeca Turbine Engines - Arrius Series","content":"### Turbomeca Turbine Engines - Arrius Series\n\n| AD/ARRIUS/12 | Check-Valve Piston O-Ring | 12/2005 |\n| ------------ | ------------------------- | ------- |\n\n| Applicability: | TURBOMECA ARRIUS 2B1/2B1A, 2B2, 2K1 and 2K2 turboshaft engines.Note 1: These engines are fitted but not limited to Eurocopter EC135 TI, T2, and Agusta A 109 Power and A 109 LUH rotorcraft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | 1. Replace the check-valve piston o-ring in accordance with paragraph 2 of Alert Service Bulletin (ASB) No. A319 79 2832 (ARRIUS 2B1/2B1A/2B2) dated 21 June 2005 or ASB No. A319 79 2833 (ARRIUS 2K1/2K2) or later DGAC approved revisions.2. Repeat Requirement 1 of this Directive.Note 2: DGAC AD F-2005-159 EASA approval No. 2005-6223 dated 6 September 2005 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Compliance:    | 1. Unless previously accomplished initial replacement of the o-ring is to be accomplished within 50 operating hours from the effective date of this Directive for engines that exceed:- 300 operating hours at the effective date of this Directive for engines operating with HTS-class oil and engines for which the history of the oils used is not available or engines which used to operate with HTS-class oil and which no longer do so;- 450 operating hours at the effective date of this Directive for engines operating with STD class-oil since their introduction into service.2. At intervals not to exceed:- 300 operating hours for engines operating with HTS-class oil and engines for which the history of the oils used is not available or engines which used to operate with HTS-class oil and which no longer do so;- 500 operating hours for engines operating with STD class-oil since their introduction into service. |\n|                | This Airworthiness Directive becomes effective on 24 November 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n\n| Background: | Investigation of incidents which occurred on ARRIUS 2 turboshaft engines has revealed that the interruption of engine lubrication was due to oil passage blockage within the lubrication unit check valve. This blockage comes from the excessive swelling of the check valve piston o-ring. The level of swelling of the o-ring depends upon which class of the oil (STD or HTS) is used and the engine operating time.A simultaneous interruption of the lubrication on both engines may lead to a double uncommanded in-flight shutdown. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJayaprakashan Ambali  \nDelegate of the Civil Aviation Safety Authority\n\n6 October 2005","sortOrder":0},{"sectionNumber":"AD/ARRIUS/12","sectionType":"part","heading":"AD/ARRIUS/12","content":"## AD/ARRIUS/12","sortOrder":1},{"sectionNumber":"Check-Valve Piston O-Ring","sectionType":"part","heading":"Check-Valve Piston O-Ring","content":"## Check-Valve Piston O-Ring","sortOrder":2},{"sectionNumber":"12/2005","sectionType":"part","heading":"12/2005","content":"## 12/2005","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The instrument targets the specified Turbomeca Arrius 2 variants and mandates o‑ring replacement per the cited Alert Service Bulletins and DGAC approvals. It does not expand applicability beyond the listed engine models or change the technical remedy; it formalises required maintenance timing tied to oil class and engine hours (Applicability; Requirement; Compliance)."},"complexity_factors":["Different compliance schedules depending on oil class (STD vs HTS) and engine operating hours (Compliance).","Staggered initial compliance windows (e.g. within 50 operating hours for engines exceeding specified hour thresholds) and recurring intervals (Compliance).","Obligation to follow specific Alert Service Bulletins or later DGAC‑approved revisions (Requirement) creates dependence on external technical documents.","Treatment of engines with unknown oil history as higher‑risk, which imposes stricter timing and record‑checking duties on operators (Compliance).","Applicability covers several Arrius 2 variants and numerous rotorcraft types, requiring operators to identify affected fleet items (Applicability).","Cross‑references to DGAC AD and EASA approval add regulatory layering that operators and maintainers must track (Requirement: DGAC AD F-2005-159; EASA approval No. 2005-6223).","Performance risk context (simultaneous dual-engine shutdown) drives a preventive maintenance remedy rather than an inspection-only approach (Background), shifting cost to operators."],"plain_english_summary":"Requires replacement and recurring replacement of the check-valve piston o-ring on Turbomeca Arrius 2B1/2B1A, 2B2, 2K1 and 2K2 engines, following the manufacturer’s Alert Service Bulletin or later DGAC‑approved revisions. Intervals and initial deadlines depend on oil class (STD or HTS) and engine operating hours. \n\nThis affects operators of rotorcraft fitted with those engines, who pay for parts and maintenance to address oil‑related o‑ring swelling that can block lubrication and risk double in‑flight shutdowns (Background; Requirement; Compliance)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, targeted Airworthiness Directive addressing a specific mechanical defect. The scope remains precisely focused on the identified safety issue (O-ring swelling causing oil blockage) without expansion into broader regulatory areas."},"complexity_factors":["Multiple engine variants covered (2B1/2B1A/2B2/2K1/2K2) with slightly different service bulletins","Conditional compliance deadlines based on two variables: accumulated operating hours AND oil classification (HTS vs STD)","Cross-reference to French aviation authority (DGAC) and European Aviation Safety Agency (EASA) documentation","Nested conditions for repeat intervals (300 hours for HTS/unknown history vs 500 hours for STD)","Technical aviation terminology requiring domain knowledge (turboshaft, operating hours, service bulletins)"],"plain_english_summary":"This AD orders operators of helicopters with Turbomeca Arrius 2-series engines (including Eurocopter EC135 and Agusta A109 Power/LUH) to replace a check‑valve piston O‑ring and carry out repeated replacements at set intervals. A swollen O‑ring can block oil flow and cause complete engine lubrication loss — risking double in‑flight engine shutdown. Compliance timing varies by engine hours and oil type."}},"importantCases":[],"_links":{"self":"/api/acts/ad-arrius-12-check-valve-piston-o-ring","history":"/api/acts/ad-arrius-12-check-valve-piston-o-ring/history","analysis":"/api/acts/ad-arrius-12-check-valve-piston-o-ring/analysis","conflicts":"/api/acts/ad-arrius-12-check-valve-piston-o-ring/conflicts","importantCases":"/api/acts/ad-arrius-12-check-valve-piston-o-ring/important-cases","documents":"/api/acts/ad-arrius-12-check-valve-piston-o-ring/documents"}}